Field of the Disclosure
The present disclosure relates to a patch antenna including a radiation electrode and a cavity.
Description of the Related Art
In a patch antenna in which a ground conductor plate is disposed on one surface of a dielectric substrate and a radiation electrode is disposed on another surface, the use of a high permittivity substrate can achieve size reduction in the antenna. When the permittivity of the dielectric substrate is increased, the band width becomes narrow and the possibility of generation of an electromagnetic wave (surface wave) propagating in an in-plane direction in the dielectric substrate is increased. When the surface wave is generated, a radiation pattern of the patch antenna is deformed and a gain in a desired direction is decreased.
Increasing the thickness of the dielectric substrate can widen the band width. However, when the thickness of the dielectric substrate is increased, the possibility of the generation of a surface wave is also increased.
Patent Document 1 discloses a patch antenna in which a resonator (cavity) is configured by arranging a plurality of conductive vias so as to surround a radiation electrode. Because a surface wave does not easily leak out of the cavity, the generation of a surface wave can be suppressed. The cavity operates as a dielectric resonator that resonates in a design frequency band of the radiation electrode. The coupling of the radiation electrode with the cavity leads to an extended band width of the patch antenna.
Patent Document 2 discloses an antenna device in which a bowtie antenna and a cavity are coupled. The use of the resonance of the cavity can achieve frequency characteristics in which an antenna gain sharply declines in a specific frequency band. Such frequency characteristics are effective for reducing radio interference with, for example, earth exploration-satellite service or radio astronomy service. In this antenna device, the generation of a surface wave can also be suppressed by disposing the cavity.
Patent Document 3 discloses a composite right/left-handed (CRLH) resonate antenna in which a microstrip patch (radiation electrode) is capacitively coupled to a ring mushroom structure. The capacitive coupling of the microstrip patch to the ring mushroom structure achieves extension of the band width and increase in the gain.
Patent Document 4 discloses an antenna device in which an electromagnetic band gap (EBG) structure is disposed on each of both sides of a radiation electrode in a microstrip antenna (patch antenna). The EBG structure includes a plurality of rows of metal patches. The use of the EBG structure can suppress unnecessary radiation and reduce feeding loss.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-61754    Patent Document 2: International Publication No. 2007-055028    Patent Document 3: Korean Patent Application Publication No. 2013-0028993    Patent Document 4: Japanese Unexamined Patent Application Publication No. 2008-283381